Ring molded article manufacturing method

ABSTRACT

A ring molded article manufacturing method capable of reliably and efficiently producing a ring molded article in which dead metal regions are reduced, is provided. In the present invention, a material is processed by first forging so as to be shaped in a shape including a bottom which is formed in a substantially disk shape, and a peripheral wall which is inclined to a direction from a center of the bottom toward an outer periphery thereof, in a direction from the outer periphery of the bottom toward one side in a direction of a center axis of the bottom, the bottom of a first forged article obtained by the first forging is drilled, a drilled article obtained by the drilling is ring-rolled, a ring material obtained by the ring rolling is placed inside two molds, the ring material is then processed by second forging so as to be pressed by the two molds in a direction of a center axis of the ring material, and the ring molded article is thus produced.

TECHNICAL FIELD

The present invention relates to a ring molded article manufacturing,method is which forging is used.

BACKGROUND ART

For example, in an engine used for an aircraft or the like, a pluralityof turbine disks are arranged side by side such that their center axesare positioned along one another, and a plurality of turbine blades areattached to each turbine disk so as to be apart from one another in adirection of a circumference of each turbine disk. In particular, in anengine used in an aircraft, high-temperature and high-pressurecombustion gas, which is generated inside the engine, flows in adirection of the center axes from a front stage side of the turbinedisks toward a rear stage side thereof, on peripheral portions of theturbine disks, and thus, the turbine disks, together with the turbineblades, rotate at a high speed around their center axes. The drivingforce generated by this rotation is transmitted to a compressor and fanswhich are located on the front stage side of the turbine disks in thedirection of the center axes, and compressed air necessary forcontinuous combustion of the gas and propulsion are thus obtained.

Generally, a turbine disk is produced by an operation in which a moldingarticle formed in a substantially ring-like shape (hereinafter referredto as a “ring molded article”), is subjected to cutting or the like. Inthis ring molded article, typically, convex portions respectivelyprotrude on both sides of the ring molded article in a direction of acenter axis thereof, and furthermore, the convex portions extend in adirection of a circumference of the ring molded article.

An outer periphery of the turbine disk is exposed to combustion gas, anda temperature thereat becomes as high as approximately 600 degrees C. to700 degrees C. Meanwhile, a temperature at an inner periphery thereof islower than that at the outer periphery. Thermal stress is generated inan inside of this turbine disk because the engine is repeatedly startedand stopped. Therefore, it is desired for the turbine disk to haveexcellent low cycle fatigue characteristics. Furthermore, centrifugalforce is applied to the outer periphery of the turbine disk according toa high-speed rotation around the axis thereof at high temperatures.Therefore, it is desired for the turbine disk to further have a highcreep strength characteristic. In addition, it is desired for theturbine disk to have a high tensile strength and a high yield strength.Therefore, it is desired for the ring molded article used in the turbinedisks, to have a sufficiently high mechanical strength appropriate forthe above desires.

Accordingly, in an example of a ring molded article manufacturingmethod, the following is performed to secure mechanical strengths of aring molded article. A cylindrical billet is processed by first forgingso as to be pressed by two molds from a direction of a center axis ofthe billet, and a first forged article which is formed in a disc-likeshape, is thus produced. The first forged article is drilled such that athrough hole in an axial direction of the forged article is formed, anda drilled article is thus produced. The drilled article is processed byring rolling, and a material which is formed in a substantiallyring-like shape (hereinafter referred to as a “ring material”), is thusproduced. Next, the ring material is placed inside the two molds onwhich concave portions corresponding to the convex portions of the ringmolded article are formed respectively, and the ring material is thensubjected to second forging so as to be sandwiched and pressed betweenthe two molds. In the second forging process, the ring material in theform of fluid fills in the concave portions of the two molds to form theconvex portions of the ring molded article, and the ring molded articleis thus obtained (for example, see Patent Literatures 1 and 2). In thesecond forging, strain is imparted to the ring molded article, thecrystal grains which form the ring molded article, are thus refined, andthereby, mechanical strengths, such as a tensile strength and a fatiguestrength, can be in particular improved. For equipment used for thesecond forging, a hydraulic-control forging press machine which canstrictly control a speed of the forging, has often been used. Inaddition, the ring molded articles produced by the example of the abovemanufacturing method, have often been used for producing large turbinedisks.

CITATION LIST Patent Literature

Patent Literature 1: JP S52-131967 A

Patent Literature 2: JP 2011-079043 A

SUMMARY OF INVENTION Technical Problem

However, in the above example of the ring molded article manufacturingmethod, it is necessary to remove a large amount of the material of thefirst forged article to form a through hole in the first forged articlewhich is formed in a cylindrical shape. This causes a problem in a viewof efficiently producing the ring molded article.

In addition, regarding the second forging process, it becomes difficultto impart strain to a surface region of the ring material which is incontact with the molds, particularly in an initial stage of the secondforging, because the material adheres to the molds. Furthermore, in thesecond forging process, a temperature of the surface region of the ringmaterial which is in contact with the molds, is decreased in comparisonwith a temperature of a central region of the ring material according toinfluence from heat release to the mold which is primarily made of ametal. According to these factors, a region of the ring molded articlecorresponding to the surface region which is in contact with the moldparticularly at the initial stage of the second forging, may have arough structure in comparison with the structure of the central regionof the ring molded article, and thus, it becomes difficult for thisregion to obtain desired mechanical characteristics. The above region isknown as a “dead metal” region. It is desired to avoid this dead metalremaining in a region of the ring molded article which is used as aturbine disk (hereinafter referred to as a “turbine disk region”). Toprevent the turbine disk region from including the dead metal region, anexcess portion of the ring molded article is previously provided suchthat a thickness thereof is increased, and the excess portion is thenremoved by a cutting after the second forging.

However, in the above example of the ring molded article manufacturingmethod, at start of the second forging and at the initial stage of thesecond forging, the ring material, which is placed inside the two molds,is in contact with an entirety of regions which range from an opening ofthe concave portion of the mold to both inner peripheral and outerperipheral sides of the concave portion, respectively. As a result, itbecomes difficult to impart strain to a wide range of the surface regionof the ring material, a temperature in a wide range of the surfaceregion of the ring material may easily decrease, and thus, the deadmetal regions may be increased in the ring molded article which isproduced in the above manner. It is necessary to increase an amount ofthe excess portions of the ring molded article corresponding to the deadmetal regions and then remove large amounts of excess portions.Accordingly, it is desired to provide near-net-shape forging in whichthe dead metal regions can be reduced so that the excess portions can bereduced.

Furthermore, in the above example of the ring molded articlemanufacturing method, it is difficult for the ring material in the formof fluid to fill an inside of the concave portion of the mold in thesecond forging process, if the two convex portions of the ring moldedarticle to be produced, are offset relative to each other in a radialdirection of the ring molded article. As a result, it becomes difficultto form the convex portions of the ring molded article, it becomesdifficult to produce the ring molded article, and thus, a problemarises.

The present invention has been made in consideration of theabove-described circumstances, and an object of the present invention isto provide a ring molded article manufacturing method capable ofreliably and efficiently producing a ring molded article in which deadmetal regions are reduced.

Solution to Problem

To solve the above-described problem, according to a ring molded articlemanufacturing method is an aspect of the present invention, the methodincludes a step of performing first forging on a material such that thematerial is formed in a shape including a bottom which is formed in adisk shape, and a peripheral wall which is inclined to a direction froma center of the bottom toward an outer periphery thereof, in a directionfrom an outer periphery of the bottom toward one side in a direction ofa center axis of the bottom, a step of drilling the bottom of a firstforged article obtained by the step of performing the first forging, astep of ring-rolling a drilled article obtained by the step of drilling,and a step of producing a ring molded article in which a ring materialobtained by the step of ring-rolling, is placed inside two molds, thering material is then processed by second forging so as to be pressed bythe two molds in a direction of a center axis of the ring material, andthe ring molded article is thus produced.

Advantageous Effects of Invention

According to the ting molded article manufacturing method in an aspectof the present invention, the ring molded article in which dead metalregions are reduced, can be reliably and efficiently produced.

BRIEF DESCRIPTION Of DRAWINGS

FIG. 1 is a plan view schematically showing a ring molded article whichis produced by a manufacturing method according to a First Embodiment ofthe present invention.

FIG. 2. is a half sectional view of the ring molded article which isproduced by the manufacturing method according to the First Embodimentof the present invention.

FIG. 3 is a flow chart for explaining the manufacturing method accordingto the First Embodiment of the present invention.

FIG. 4 is a full sectional view schematically showing a billet to besubjected to rough forging in the manufacturing method according to theFirst Embodiment of the present invention.

FIG. 5 is a plan view schematically showing a rough-forged article madeby rough forging in the manufacturing method according to the FirstEmbodiment of the present invention.

FIG. 6 is a full sectional view schematically showing a drilled articlemade by a drilling process in the manufacturing method according to theFirst Embodiment of the present invention.

FIG. 7 is a diagram for explaining ring rolling in the manufacturingmethod according to the First Embodiment of the present invention.

FIG. 8(a) is a half sectional view schematically showing a condition ofarrangement of a ring-rolled article immediately before start offinishing forging in the manufacturing method according to the FirstEmbodiment of the present invention.

FIG. 8(b) is a half sectional view schematically showing a conditionimmediately after the finishing forging is completed.

FIG. 9 is a half sectional view schematically showing the ring-rolledarticle of FIG. 8(a).

DESCRIPTION OF EMBODIMENTS

A method for manufacturing a ring molded article according to First toThird Embodiments of the present invention will be described below withreference to FIGS. 1 to 9. Note that in the First to Third Embodimentsof the present invention, the following expressions are used for asection of an article which is substantially symmetric based on a centeraxis (hereinafter referred to as a “symmetric article”), and drawingswhich show such sections. Among sections obtained by cutting a symmetricarticle along a plane passing through the center axis, one of which willbe referred to as a “half section”, and a drawing, such as FIGS. 2, 8,and 9, showing this half section will be referred to as a “halfsectional view”. An entire section of a symmetric article obtained bycutting the symmetric article along a plane passing through the centeraxis will be referred to as a “full section”, and a drawing, such asFIGS. 4 to 6, showing this full section will be referred to as a “fullsectional view”.

First Embodiment

A ring molded article produced by a manufacturing method according tothe First Embodiment of the present invention will be described below. Aring molded article is used for producing a turbine disk in an enginefor an aircraft or the like. Furthermore, the turbine disk is producedby an operation in which a ring molded article after molding isprocessed by heat treatment, an operation in which an excess portion ofa ring molded article is removed, and the like. Typically, a ring moldedarticle is made of metals, and in the present Embodiment, a ring moldedarticle is produced of Ni-base alloy718. However, the present inventionis not limited to this. More specifically, any metal which enablesmanufacturing of a ring molded article having high strength at hightemperatures, can be used. As an example, a ring molded article may beproduced by using a Ni-base alloy, a Fe-base alloy, a Co-base alloy, orthe like which has high strength at high temperatures.

As shown in FIGS. 1 and 2, the ring molded article includes a baseportion 1 b which is formed in a substantially ring-like shape around acenter axis 1 a thereof. The ring molded article 1 includes a one sideconvex portion 1 c and an another side convex portion 1 d which protrudefrom the base portion 1 b on both sides of the ring molded article 1 ina center axis direction thereof, respectively. The two convex portions 1c and 1 d are formed so as to extend in a direction of a circumferenceof the ring molded article 1. Note that in FIG. 2, the one side convexportion 1 c and the another side convex portion 1 d of the ring moldedarticle 1 substantially coincide with each other in a radial directionof the ring molded article 1. However, in an alternative feature, theone side convex portion 1 c and the another side convex portion 1 d ofthe ring molded article 1 can be offset relative to each other in theradial direction of the ring molded article 1.

An outline of the above method for manufacturing the ring molded article1 will be described with reference to FIG. 3. A billet 2 (shown in FIG.4) is subjected to rough forging as first forging, and thus, arough-forged article 3 (shown in FIG. 5) is produced as a first forgedarticle (Rough forging step S1). The rough-forged article 3 is processedby drilling so that a drilled article 4 is made (shown in FIG. 6). Notethat the drilled article 4 may be further processed by intermediate ringrolling if necessary (drilling step S2). The drilled article 4 isring-rolled so that a ring-rolled article 5 (shown in FIGS. 8(a) and 9)configured as a ring material, is made (ring rolling step S3). Thering-rolled article 5 is processed by finish forging as second forgingso that the above ring molded article 1 configured as a second forgedarticle, is made (finishing forging step S4).

Details of each step in the method for manufacturing the ring moldedarticle 1 will be described below.

Regarding the Rough Forging Step S1

Details of the rough forging step S1 will be described below. As shownin FIG. 4, the billet 2 formed in a substantially cylindrical shapearound a center axis 2 a as a material to be processed by rough forging,is produced by using Ni-base alloy718, and then, the billet 2 is pressedby using molds and the like so that the rough-forged article 3 shown inFIG. 5 is produced. As an example, if the billet 2 is to be produced byusing Ni-base alloy 718, it is preferable that a heating temperature forthe billet 2 used in the rough forging step S1 be in a range of 900degrees C. to 1075 degrees C. However, the present invention is notlimited to this. More specifically, if the billet 2 is to be produced byusing a metal other than Ni-base alloy718, the heating temperature maybe set so as to be adapted to rough forging which is performed on theabove billet.

As shown in FIG. 5, the rough-forged article 3 is formed so as toinclude a bottom 3 b which is formed in a substantially disc-like shapearound a center axis 3 a, and a peripheral wall 3 c which is inclined toa direction from a center of the bottom 3 b to an outer peripherythereof, in a direction from the center of the bottom 3 b to one side ofa center axis direction of the bottom 3 b. Note that in FIG. 5, a brokenline indicates a boundary between the bottom 3 b and the peripheral wall3 c. In the drilling process described below, the bottom 3 b is removedalong the broken line. In the above rough-forged article 3, if a halfsection of the peripheral wall 3 c is divided into a one side region 3 eand an another side region 3 f in a center axis direction of therough-forged article 3 based on a middle line 3 d for a maximum height h1 of the rough-forged article 3 in the center axis direction thereof, astraight line 3 i which passes through a center of gravity 3 g of theone side region 3 e and a center of gravity 3 h of the another sideregion 3 f, is inclined by an angle •1 relative to a parallel line 3 jwhich is in parallel with the center axis 3 a of the rough-forgedarticle 3, i.e., relative to the center axis 3 a of the rough-forgedarticle 3. It is preferable that the angle •1 be in a range which is 7degrees to 40 degrees.

Regarding Drilling Step S2

Details of the drilling step S2 will be described below. Therough-forged article 3 is processed by drilling, such as punching outwith press working, cutting with a water cutter, or the like, such thatthe bottom 3 b of the rough-forged article 3 shown in FIG. 5 is removed.As a result, the drilled article 4 including a through hole 4 b which isformed along a center axis 4 a, is produced as shown in FIG. 6. Thedrilled article 4 includes a peripheral wall 4 c corresponding to theperipheral wall 3 c of the rough-forged article 3. If necessary, thedrilled article 4 may be processed by intermediate ring rolling.

Regarding Ring Rolling Step S3

The ring rolling step S3 will be described below. In the ring rollingstep S3, as an example, a ring rolling apparatus 11 shown in FIG. 7 isused. The ring rolling apparatus 11 includes a main roll 12 which islocated on an outer periphery side of the drilled article 4, and amandrel roll 13 which is located on an inner periphery side of thedrilled article 4. The outer peripheral surface of the main roll 12 andthat of the mandrel roll 13 face each other. The main roll 12 isconfigured so as to be rotatable around a rotational axis 12 a whichpasses through a center of the main roll 12 and extends substantiallyparallel with the center axis 4 a of the drilled article 4. The outerperipheral surface of the main roll 12 is inclined so as to correspondto an outer peripheral surface of the ring-rolled article 5 to beproduced. The mandrel roll 13 is also configured so as to be rotatablearound a rotational axis 13 a which passes through the center of themandrel roll 13 and extends substantially in parallel with the centeraxis 4 a of the drilled article 4. The outer peripheral surface of themandrel roll 13 is inclined so as to correspond to an inner peripheralsurface of the ring-rolled article 5 to be produced. However, thepresent invention is not limited to this. More specifically, the mainroll and the mandrel roll may be formed in a substantially cylindricalshape and the rotational axis of the main roll and the mandrel roll maybe respectively arranged so as to be inclined in correspondence with theouter peripheral surface and the inner peripheral surface in thering-rolled article 5 to be produced. In addition, the ring rollingapparatus 11 includes a pair of axial rolls 14, 15 located on both sidesof the drilled article 4 in a center axis direction thereof. An outerperipheral surface of the axial roll 14 and that of the axial roll 15face each other. Each of the axial rolls 14, 15 is configured so as tobe rotatable around a rotational axis 14 a, 15 a which passes throughthe center of the corresponding axial roll.

In the ring rolling step S3 in which the above ring rolling apparatus 11is used, first, the drilled article 4 is charged into the ring rollingapparatus 11. As an example, if the drilled article 4 is to be producedby using Ni-base alloy718, it is preferable that a heating temperaturefor the drilled article 4 to be charged into the ring rolling apparatus11, be in a range of 900 degrees C. to 1050 degrees C. However, thepresent invention is not limited to this. More specifically, if thedrilled article 4 is to be produced by using a metal other than Ni-basealloy718, the heating temperature may be set so as to be adapted to ringrolling performed on the above drilled article 4. The outer peripheralsurface of the main roll 12 is brought into contact with the outerperipheral surface of the drilled article 4, the outer peripheralsurface of the mandrel roll 13 is brought into contact with the innerperipheral surface of the drilled article 4, and furthermore, the outerperipheral surfaces of the axial roll pair 14, 15 are respectivelybrought into contact with both surfaces of the drilled article 4 in thecenter axis direction thereof. While the main roll 12 and the mandrelroll 13 are turned around the rotational axis 12 a, 13 a, respectively,the main roll 12 and the mandrel roll 13 sandwich and press the drilledarticle 4 in a radial direction of the drilled article 4. In addition,while the axial rollers 14, 15 are turned around the rotational axis 14a, 15 a, respectively, the pair of axial rolls 14, 15 sandwich and pressthe drilled article 4 in the center axis direction of the drilledarticle 4. As a result, the ring-rolled article 5 is produced.

The ring-rolled article 5 is formed so as to be shaped in asubstantially ring-like shape around a center axis 5 a of thering-rolled article 5, and a half section of the ring-rolled article 5is formed so as to be inclined. More specifically, as shown in FIG. 9,if the half section of the ring-rolled article 5 is divided into a oneside region 5 c and an another side region 5 d in a center axisdirection of the ring-rolled article 5 based on a middle line 5 b for amaximum height h2 of the ring-rolled article 5 in the center axisdirection thereof, a straight line 5 g which passes through a center ofgravity 5 e of the one side region 5 e and a center of gravity 5 g ofthe another side region 5 d, is inclined by an angle •2 relative to aparallel line 5 h which is in parallel with the center axis 5 a of thering-rolled article 5, i.e. relative to the center axis 5 a of thering-rolled article 5. It is preferable that the angle •2 be in a rangeof 7 degrees to 40 degrees. Furthermore, it is more preferable that theangle •2 be in a range of 10 degrees to 25 degrees. This is because ifthe angle •2 is in the above range, sufficient amount of strain can beimparted to the material in the finishing forging step S4 describedbelow so that the material may be appropriate, particularly as amaterial for aircraft turbine disks. The angle •2 in the one halfsection of the ring-rolled article 5 may be either the same as ordifferent from the angle •1 in the one half section of the peripheralwall 3 c of the rough-forged article 3. If the angle •2 is differentfrom the angle •1, the drilled article 4 may be ring-rolled: such thatthe above angle is changed.

In addition, as an example, the outer peripheral surface of thering-rolled article 5 may be formed in a substantially arc-like shapewhich protrudes from the inner periphery of the ring-rolled article 5toward the outer periphery thereof. Furthermore, to form the outerperipheral surface of the ring-rolled article 5 which is formed in thesubstantially arc-like shape, the outer peripheral surface of the mainroll 12 may be formed in a substantially arc-like shape which recessesfrom the inner periphery of the ring-rolled article 5 toward outerperiphery thereof so as to correspond to the outer peripheral surface ofthe ring-rolled article 5. The inner peripheral surface of thering-rolled article 5 may be formed in a substantially arc-like shapewhich protrudes from the outer periphery of the ring-rolled article 5 tothe inner periphery thereof. Furthermore, to form the inner peripheralsurface of the ring-rolled article 5 which is formed in theabove-described substantially arc-like shape, the outer peripheralsurface of the mandrel roll 13 may be formed in a substantially arc-likeshape which recesses from the outer periphery of the ring-rolled article5 to the inner periphery thereof so as to correspond to the innerperipheral surface of the ring-rolled article 5.

Regarding Finishing Forging Step S4

The finishing forging step S4 will be described below. In the finishingforging step S4, a one side mold 16 and an another side mold 17, shownin FIGS. 8(a) and 8(b), are used. The one side mold 16 includes aconcave portion 16 a which corresponds to the one side convex portion 1c of the ring molded article 1, and an opening side concave portion 16 bwhich corresponds to the one side region in the base portion 1 b of thering molded article 1. The another side mold 17 includes a concaveportion 17 a which corresponds to the another side convex portion 1 d ofthe ring molded article 1, and an opening side concave portion 17 bwhich corresponds to the another side region of the base portion 1 b ofthe ring molded article 1.

In the finishing forging step S4, the ring-rolled article 5 is placed inthe above two molds 16, 17, and then, the ring-rolled article 5 issandwiched and pressed by the two molds 16, 17 in a center axis divisionof the ring-rolled article 5. As an example, if the ring-rolled article5 is produced by using Ni-base alloy718, it is preferable that a heatingtemperature for the ring-rolled article 5 placed in the two molds 16, 17be in a range of 900 degrees C. to 1050 degrees C. However, the presentinvention is not limited to this. More specifically, if the ring-rolledarticle 5 is produced of a metal other than Ni-base alloy718, theheating temperature may be set to a temperature adapted to the finishingforging performed on the ring-rolled article 5.

In conditions in which the above ring-rolled article 5 is arranged, thering-rolled article 5 is supported by a region which is located on theouter peripheral side from an outer peripheral side corner 16 c in aconcave portion 16 a of the one side mold 16 (this region will behereafter be referred to as an “outer peripheral side supportingregion”), and a region which is located on the inner peripheral sidefrom an inner peripheral side corner 17 c in a concave portion 17 a ofthe another side mold 17 (this region will he hereafter referred to asan “inner peripheral side supporting region”) Note that the aboveexpression “outer peripheral side corner 16 c in the concave portion 16a” indicates a corner located between an outer peripheral surface 16 a 1in the concave portion 16 a of the one side mold 16 and an outerperipheral side bottom surface 16 b 1 in the opening side concaveportion 16 b thereof, and the above expression “inner peripheral sidecorner 17 c in the concave portion 17 a” indicates a corner locatedbetween an inner peripheral surface 17 a 1 in the concave portion 17 aof the another side mold 17 and an inner peripheral side bottom surface17 b 1 in the opening side concave portion 17 b thereof. Furthermore, itis preferable that the ring-rolled article 5 be arranged so as to beapart from regions other than the outer peripheral side supportingregion of the one side mold 16 and the inner peripheral side supportingregion of the another side mold 17. In other words, both ends of thering-rolled article 5 in a direction of the inclined straight line 5 gare in contact with the two molds 16, 17, respectively, and thering-rolled article 5 is restricted by the two molds 16, 17 in thecenter axis direction of the ring-rolled article 5 and in the radialdirection of the ring-rolled article 5.

In particular, in the present Embodiment, as shown in FIG. 8(a), thering-rolled article 5 is supported by the outer periphery side bottomsurface 16 b 1 and the outer peripheral surface 16 b 2 in the openingside concave portion 16 b of the one side mold 16 and the innerperipheral side bottom surface 17 b 1 and the inner peripheral surface17 b 2 in the opening side concave portion 17 b of the another side mold17. Furthermore, it is preferable that the ring-rolled article bearranged so as to be apart from regions other than the outer peripheryside bottom surface 16 b 1 and the outer peripheral surface 16 b 2 inthe opening side concave portion 16 b of the one side mold 16 and theinner peripheral side bottom surface 17 b 1 and the inner peripheralsurface 17 b 2 in the opening side concave portion 17 b of the anotherside mold 17.

Furthermore, in the finishing forging, the ring-rolled article 5 in theform of fluid fills the concave portion 16 a and the opening sideconcave portion 16 b of the one side mold 16 and the concave portion 17a and the opening side concave portion 17 b of the another side mold 17.As a result, the ring molded article 1 is produced.

According to the above method for manufacturing the ring molded article1 in the present Embodiment, the billet 2 is processed by the roughforging so as to be formed in a shape including the bottom 3 b which isfarmed in the substantially cylindrical shape, and the peripheral wall 3c which is inclined to the direction from the center of the bottom 3 btoward the outer periphery thereof, in the direction from the outerperiphery of the bottom 3 b toward the one side in the direction of thecenter axis of the bottom 3 b, the rough-forged article 3 is thusproduced, and the bottom 3 b of the rough-forged article 3 is drilled.Furthermore, the ring-rolled article 5 is placed in the two molds 16, 17on which the concave portions 16 a, 17 a respectively corresponding tothe convex portions 1 c, 1 d of the ring molded article 1, thering-rolled article 5 is then processed by the finishing forging so thatthe ring-rolled article 5 is pressed by the two molds 16, 17 in thedirection of the center axis of the ring-rolled article 5, and the ringmolded article 1 is thus produced. In particular, in the finishingforging step S4, when placing the ring-rolled article 5 in the two molds16, 17, the ring-rolled article 5 is supported by the outer peripheryside supporting region of the one side mold 16 and the inner peripheralside supporting region of the another side mold 17, and furthermore, thering-rolled article 5 is arranged so as to be apart from the regionsother than the outer periphery side supporting region of the one sidemold 16 and the inner peripheral side supporting region of the otherside mold 17. An outer peripheral shape of the rough-forged article 3 istapered from a top thereof to the bottom 3 b thereof, and dimension areaof the bottom 3 b can be reduced. As a result, an amount of the bottom 3b to be removed in the drilling step S2 can be reduced. Accordingly, thering molded article 1 can be efficiently produced. In addition, in thefinishing forging step S4, the contact area between the ring-rolledarticle 5 and the two molds 16, 17 can be reduced, and as a result,regions that the material of the ring-rolled article 5 adhere to the twomolds 16, 17, can be reduced at the start of the finishing forging andthe initial stage of the finishing forging, and thus, sufficient straincan be imparted to the ring molded article 1 to be produced. Inaddition, it can be prevented that the temperature of the surfaceregions of the ring-rolled article 5 is reduced according to heatrelease to the two molds 16, 17, and thus, it can be prevented thatcrystals of metal structure in the surface regions of the produced ringmolded article 1 is coarsened. Accordingly, the ring molded article 1 inwhich dead metal regions are reduced, can be reliably and efficientlyproduced. In addition, the excess portions of the ring molded article 1which is provided in correspondence with the dead metal regions, can bereduced, and thus, near-net-shape forging can be implemented.Furthermore, even if the one side convex portion 1 c and the anotherside convex portion 1 d of the ring molded article 1 are offset relativeto each other in the radial direction of the ring molded article 1, thering-rolled article 5 in the form of fluid securely fills into theconcave portions 16 a, 17 a of the two melds 16, 17, and thus, the twoconvex portions 1 c, 1 d of the ring molded article 1 can be securelyformed.

According to the method for manufacturing the ring molded article 1 inthe present Embodiment, the inclination angle •1 of the one half sectionof the peripheral wall 3 e is within the range of 7 degrees to 40degrees. Accordingly, since the inclination angle •1 is 7 degrees ormore, in the finishing forging step S4, buckling of the ring-rolledarticle 5 can be prevented. Furthermore, since the inclination angle •1is 40 degrees or less, the size of the rough-forged article 3 can bereduced, and furthermore, in the finishing forging step S4, a phenomenonin which a desired shape cannot be obtained according to unstablefinishing forging caused by turning of the ring-rolled article 5 (thisphenomenon will hereafter be referred to as “phenomenon of turning ofthe ring-rolled article 5”), can be prevented. Accordingly, the ringmolded article 1 in which the dead metal regions are reduced, can bereliably and efficiently produced.

According to the method for manufacturing the ring molded article 1 inthe present Embodiment, the inclination angle •2 of the ring-rolledarticle 5 which is placed in the two molds 16, 17, is within the rangeof 7 degrees to 40 degrees, at the start of the finishing forging andthe initial stage of the finishing forging. Accordingly, since theinclination angle •2 is 7 degrees or more, in the finishing forging stepS4, buckling of the ring-rolled article 5 can be prevented. Furthermore,since the inclination angle •2 is 40 degrees or less, the phenomenon ofturning of the ring-rolled article 5 can be prevented. Accordingly, thering molded article 1 in which the dead metal regions are reduced, canbe reliably and efficiently produced.

Second Embodiment

A method for manufacturing a ring molded article according to a SecondEmbodiment of the present invention will be described. Basic features ofthe ring material used for manufacturing the ring molded articleaccording to the present Embodiment are substantially the same as thoseof the First Embodiment described above. However, the method formanufacturing the ring molded article according to the presentEmbodiment is different from the method of the First Embodiment in thefollowing.

Although not shown in the drawing, in the ring-rolled article configuredas the ring material, a recess section is formed so as to correspond tothe outer peripheral side corner of the concave portion in the one sidemold. As an example, the recess section may be formed by machineworking, such as cutting, press working, or the like, after the ringrolling. In the finishing forging step, this ring-rolled article issupported by the outer peripheral side corner in the concave portion ofthe one side mold which engages the recess section, and also supportedby the inner peripheral side bottom surface and the inner peripheralsurface in the opening side concave portion of the another side mold.Furthermore, it is preferable that the ring-rolled article be arrangedso as to be apart from regions other than the outer peripheral sidecorner in the concave portion of the one side mold and the innerperipheral side bottom surface and the inner peripheral surface in theopening side concave portion of the another side mold.

According to the above method for manufacturing the ring molded articlein the present Embodiment, in addition to the advantageous effectsobtained by the First Embodiment, the following advantageous effects canbe obtained. That is to say, since the recess section of the ring-rolledarticle engages the outer peripheral side corner in the concave portionof the one side mold, the ring-rolled article can be stably supportedinside the two molds. Accordingly, the ring-rolled article in which thedead metal regions are reduced can be reliably and efficiently produced.

Third Embodiment

A method for manufacturing a ring molded article according to a ThirdEmbodiment of the present invention will be described. Basic features ofthe method for manufacturing the ring molded article are substantiallythe same as those of the First Embodiment described above. However, themethod for manufacturing the ring molded article according to thepresent Embodiment is different from the method of the First Embodimentin the following.

Although not shown in the drawing, in the ring-rolled article configuredas the ring material, recess sections are formed which respectivelycorrespond to an outer peripheral side corner in the concave portion ofthe one side mold and to an inner peripheral side corner in the concaveportion of the another side mold. As an example, the recess sections maybe formed by machine working, such as cutting, press working, or thelike, after the ring rolling. In the finishing forging step, thisring-rolled article is supported by the outer peripheral side corner inthe concave portion of the one side mold which engages the correspondingrecess section of the two recess sections, and also supported by theinner peripheral side corner in the concave portion of the another sidemold. Furthermore, it is preferable that the ring-rolled article bearranged so as to be apart from regions other than the outer peripheralside corner in the concave portion of the one side mold and the innerperipheral side corner in the opening side concave portion of theanother side mold.

According to the above method for manufacturing the ring molded articlein the present Embodiment, in addition to the advantageous effectsobtained by the First Embodiment, the following advantageous effects canbe obtained. That is to say, since the recess sections of thering-rolled article engage the outer peripheral side corner in theconcave potions of the one side mold and the inner peripheral sidecorner in the concave potions of the another side mold respectively, thering-rolled article can be stably supported inside the two molds.Accordingly, the ring-rolled article in which the dead metal regions arereduced can be reliably and efficiently produced.

The Embodiments of the present invention are as described above;however, the present invention is not limited to them. Morespecifically, the present invention can be implemented by variousmodifications and alterations based on the technical idea of the presentinvention.

For example, as a modification of the present invention, the followingfeature may be employed. That is to say, in this feature, if the concaveportions 16 a, 17 a of the two molds 16, 17 which are used in thefinishing forging step S4, are offset in the radial direction of thering molded article 1 so as to correspond to the one side convex portion1 c and the another side convex portion 1 d in the ring molded article 1which are offset in the radial direction, the ring-rolled article 5 canbe supported in a condition in which the one half section of thering-rolled article 5 is not inclined, i.e., in a condition in which theinclination angle •2 for the one half section is 0 degrees. In thisfeature, for example, the one half section of the ring-rolled article 5may be formed in a substantially rectangular shape, and furthermore, anamount of offset between the concave portions 16 a, 17 a of the twomolds 16, 17 in the radial direction of the ring-rolled article 5 may beless than a thickness of the one side surface in the radial direction ofthe ring-rolled article 5. In this feature, the ring-rolled article 5can be supported by the outer peripheral side supporting region of theone side mold 16 and the inner peripheral side sup porting region of theanother side mold 17. If the above feature is employed, the forging canbe implemented such that the phenomenon of dead metal is suppressed.However, in view of stable arrangement of the ring-rolled article 5 andfreedom of shape of the ring-rolled article 5, it is preferable toemploy the feature in which the one half section of the ring-rolledarticle is inclined.

EXAMPLE

An EXAMPLE of the present invention will be described. In the presentEXAMPLE, the ring molded article 1 to be produced has dimensions with amaximum outer diameter of 1090 mm, a maximum thickness in the radialdirection of 120 mm, and a maximum height in the direction of the centeraxis of 110 mm. In the finishing forging step S4 used for producing thisring molded article 1, the finishing forging step S4 is performed in aplurality of arrangement conditions, respectively, in which theinclination angle •2 for the inclined one half section of thering-rolled article 5 is set at 5 degrees, 7 degrees, 10 degrees, 20degrees, 25 degrees, 30 degrees, 40 degrees, 45 degrees, or 50 degrees.In the forging step for each arrangement condition, it is examinedwhether buckling of the ring-rolled article 5 occurs. In addition, inthe forging step for each arrangement condition, it is examined whetherthe phenomenon of turning of the ring-rolled article 5 occurs.

As a result of the above examination, in a ease in which the inclinationangle •2 is 5 degrees, buckling of the ring-rolled article 5 occurs. Ineach of eases in which the inclination angles •2 are 45 degrees and 50degrees respectively, the phenomenon of turning of the ring-rolledarticle 5 occurs. On the other hand, in each of cases in which theinclination angles •2 are 7 degrees, 10 degrees, 20 degrees, 30 degrees,and 40 degrees, respectively, the ring molded article 1 in which deadmetal regions are reduced, can be reliably and efficiently produced. Ineach of cases in which the inclination angles •2 are 10 degrees, 20degrees, and 25 degrees respectively, in particular, the ring moldedarticle 1 in which strain appropriate for applying to a material ofaircraft turbine disks is sufficiently imparted and the dead metalregions are reduced, can be more reliably and more efficiently produced.

REFERENCE SIGNS LIST

-   1 Ring Molded article-   1 a Center axis-   1 c One side convex portion-   1 d Another side convex portion-   2 Billet-   3 Rough-forged article-   3 a Center axis-   3 b Bottom-   3 c Peripheral wall-   3 d Middle line-   3 e One side region-   3 f Another side region-   3 g, 3 h Center of gravity-   3 i Straight line-   3 j Parallel line-   4 Drilled article-   5 Ring-rolled article (Ring material)-   5 a Center axis-   5 b Middle line-   5 e One side region-   5 d Another side region-   5 e, 5 f Center of gravity-   5 g Straight line-   5 h Parallel line-   16 One side mold-   16 a Concave portion-   16 c Outer peripheral side corner in the concave portion-   17 Another side mold-   17 a Concave portion-   17 c Inner peripheral side corner in the concave portion-   h1, h2 Maximum height-   •1, •2 Angle-   S1 Rough forging step (First forging step)-   S2 Drilling step-   S3 Ring rolling step-   S4 Finishing forging step (Second forging step)

1. A ring molded article manufacturing method comprising: a step ofperforming first forging on a material such that the material is formedin a shape including a bottom which is formed in a disk shape, and aperipheral wall which is inclined to a direction from a center of thebottom toward an outer periphery thereof, in a direction from an outerperiphery of the bottom toward one side in a direction of a center axisof the bottom; a step of drilling the bottom of a first forged articleobtained by the step: of performing the first forging; a step ofring-rolling a drilled article obtained by the step of drilling; and astep of producing a ring molded article in which a ring materialobtained by the step of ring-rolling is placed inside two molds, thering material is then processed by second forging so as to be pressed bythe two molds in a direction of a center axis of the ring material, andthe ring molded article is thus produced.
 2. The ring molded articlemanufacturing method according to claim 1, wherein the ring moldedarticle includes two convex portions which respectively protrude on bothsides of the ring molded article in a direction of a center axis thereofand extend in a direction of a circumference of the ring molded article,concave portions respectively corresponding to the convex portions ofthe ring molded article are formed on the two molds respectively, andthe ring material placed inside the two molds is supported by a regionlocated on an outer peripheral side from an outer peripheral side cornerm the concave portion of one of the two molds and a region located on aninner peripheral side from an inner peripheral side corner in theconcave portion of another of the two molds.
 3. The ring molded articlemanufacturing method according to claim 1, wherein in the step ofperforming the first forging, if a one half section of the peripheralwall is divided into a one side region and an another side region in thedirection of the center axis of the first forged article based on amiddle of a maximum height of the first forged article in the directionof the center axis of the first forged article, a straight line passingthrough a center of gravity of the one side region and a center ofgravity of the another side region is inclined by an angle relative tothe center axis of the first forged article, of which a range is 7degrees to 40 degrees.
 4. The ring molded article manufacturing methodaccording to claim 1, wherein if a one half section of the ring materialplaced inside the two molds is divided into a one side region and another side region in the direction of the center axis of the ringmaterial based on a middle of a maximum height of the ring material inthe direction of the center axis of the ring material, a straight linepassing through a center of gravity of the one side region and a centerof gravity of the another side region is inclined by m angle relative tothe center axis of the ring material, of which a range is 7 degrees to40 degrees.